Book Image

Functional Kotlin

Book Image

Functional Kotlin

Overview of this book

Functional programming makes your application faster, improves performance, and increases your productivity. Kotlin supports many of the popular and advanced functional features of functional languages. This book will cover the A-Z of functional programming in Kotlin. This book bridges the language gap for Kotlin developers by showing you how to create and consume functional constructs in Kotlin. We also bridge the domain gap by showing how functional constructs can be applied in business scenarios. We’ll take you through lambdas, pattern matching, immutability, and help you develop a deep understanding of the concepts and practices of functional programming. If you want learn to address problems using Recursion, Koltin has support for it as well. You’ll also learn how to use the funKtionale library to perform currying and lazy programming and more. Finally, you’ll learn functional design patterns and techniques that will make you a better programmer.By the end of the book, you will be more confident in your functional programming skills and will be able to apply them while programming in Kotlin.
Table of Contents (22 chapters)
Title Page
Copyright and Credits
Dedication
Packt Upsell
Contributors
Preface
Index

Introduction to Streams


As we mentioned earlier, Streams were first introduced from Java 8. Starting from Java 8, Java started to give more focus to functional programming and started to add functional features gradually.

Kotlin, on the other hand, started to add functional features from day one. Kotlin added functional features and interfaces. While working with Java, you can use Streams only if you use Java 8 and later versions, but with Kotlin you can still use Streams, even when working with JDK 6.

So, what are Streams? You can think of Streams as an abstract layer over a sequence of elements to perform aggregate operations. Confused? Let's take a code example and then try to understand:

  fun main(args: Array<String>) { 
      val stream = 1.rangeTo(10).asSequence().asStream() 
      val resultantList = stream.skip(5).collect(Collectors.toList()) 
      println(resultantList) 
  } 

The output is as follows:

In the preceding program, what we did was create an IntRange value, create...